Many companies and other organizations operate computer networks that interconnect numerous computing systems to support their operations, such as with the computing systems being co-located or instead located in multiple distinct geographical locations. For example, distributed systems housing significant numbers of interconnected computing systems have become commonplace. Such distributed systems may provide back-end services to web servers that interact with clients. Such distributed systems may also include data centers that are operated by entities to provide computing resources to customers. Some data center operators provide network access, power, and secure installation facilities for hardware owned by various customers, while other data center operators provide “full service” facilities that also include hardware resources made available for use by their customers. As the scale and scope of distributed systems have increased, the tasks of provisioning, administering, and managing the resources have become increasingly complicated.
Web servers backed by distributed systems may provide marketplaces that offer goods and/or services for sale to consumers. For instance, consumers may visit a merchant's website to view and/or purchase goods and services offered for sale by the merchant (and/or third party merchants). Some network-based marketplaces (e.g., Internet-based marketplaces) include large electronic catalogues of items offered for sale. For each item offered for sale, such electronic catalogues typically include at least one product detail page (e.g., a web page) that specifies various information about the item, such as a description of the item, one or more pictures of the item, as well as specifications (e.g., weight, dimensions, capabilities) of the item. In various cases, such network-based marketplaces may rely on a service-oriented architecture to implement various business processes and other tasks. The service-oriented architecture may be implemented using a distributed system that includes many different computing resources and many different services that interact with one another, e.g., to produce a product detail page for consumption by a client of a web server.
Load balancers may provide client access to a fleet of hosts that implement a marketplace. A load balancer may receive a request from a client and direct the client request to an appropriate one of the hosts. Various load balancing algorithms have been employed to select a host to serve a given client request; each algorithm may have advantages and disadvantages. For example, using a “least connections” algorithm, the load balancer may select the host that is currently servicing the least amount of traffic. However, a faulty host may contribute to a problem known as the “black hole effect” when the least connections algorithm is used. If the faulty host is handling requests very quickly by failing them, then a disproportionate amount of client traffic may be routed to the faulty host using the least connections algorithm. Thus a single faulty host in combination with a load balancer may cause a disproportionate amount of client requests to fail.
While embodiments are described herein by way of example for several embodiments and illustrative drawings, those skilled in the art will recognize that embodiments are not limited to the embodiments or drawings described. It should be understood, that the drawings and detailed description thereto are not intended to limit embodiments to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning “having the potential to”), rather than the mandatory sense (i.e., meaning “must”). Similarly, the words “include,” “including,” and “includes” mean “including, but not limited to.”